P0300 random misfire detected.

[miketx]

2003 trailblazer 6 cylinder. Put gas in it the other day and it just all of a sudden started running rough, misfiring. Scanned and it had P0300. Usually the computer will tell you which cylinder is misfiring, so if it's cylinder #2, it will set code P0302. So I had to do detective work. I took all the plastic crap off the top to access the 6 coil packs, started it and disconnected the coil pack wiring harnesses one at a time. disconnecting cylinders 1 - 3 made the engine run worse each time I took one loose, but when I took #4 loose, no change! Bingo! My friend brought over a used coil and I fixed it. Yay!

 

[Tijn Von Ingersleben]

 

[Cellblock2429]

2003 trailblazer 6 cylinder. Put gas in it the other day and it just all of a sudden started running rough, misfiring. Scanned and it had P0300. Usually the computer will tell you which cylinder is misfiring, so if it's cylinder #2, it will set code P0302. So I had to do detective work. I took all the plastic crap off the top to access the 6 coil packs, started it and disconnected the coil pack wiring harnesses one at a time. disconnecting cylinders 1 - 3 made the engine run worse each time I took one loose, but when I took #4 loose, no change! Bingo! My friend brought over a used coil and I fixed it. Yay!

/---/ Or you could have taken it to a national chain repair shop who would have sold you a rebuilt engine for $4,000. Good job.

 

[miketx]

2003 trailblazer 6 cylinder. Put gas in it the other day and it just all of a sudden started running rough, misfiring. Scanned and it had P0300. Usually the computer will tell you which cylinder is misfiring, so if it's cylinder #2, it will set code P0302. So I had to do detective work. I took all the plastic crap off the top to access the 6 coil packs, started it and disconnected the coil pack wiring harnesses one at a time. disconnecting cylinders 1 - 3 made the engine run worse each time I took one loose, but when I took #4 loose, no change! Bingo! My friend brought over a used coil and I fixed it. Yay!

/---/ Or you could have taken it to a national chair repair shop who would have sold you a rebuilt engine for $4,000. Good job.

That shit happens.